A typical permanent magnet direct current (PMDC) motor comprises a stator and a rotor rotatable relative to the stator. The stator comprises a housing and a plurality of permanent magnets fixed on the inner surface of the housing. The rotor comprises a shaft, a rotor core fixed to the shaft, a commutator fixed the shaft adjacent the rotor core. The rotor core comprises a plurality of teeth and slots formed between adjacent teeth. Windings are wound on the teeth of the rotor core and connected to segments of the commutator. The stator further comprises brushes in sliding electrical contact with the commutator for transferring electrical power to the windings.
However, in traditional PMDC motors, the number of the commutator segments is equal to that of the rotor slots. The size of the commutator cannot be reduced, which results in a kind of PMDC motor that is not suitable for small electric apparatus with a compact structure.
Hence there is a desire for an improved electric motor with a commutator of reduced size.